The effects of the welding methods, heat input and heat cycle on the mechanical properties at elevated temperature for the 308 type stainless steel weld metals rae investigated and the following results are obtained.
1) Creep rupture strength for the TIG arc weld metals is large about 2 kg/mm
2 compared with that for the submerged arc weld metals, and creep rupture elongation for the submerged arc weld metals is large compared with that for the TIG arc weld metals.
2) The oxygen contents of the submerged arc weld metals are more than ten times as much as those for the TIG arc weld metals. The oxygen in the weld metals forms the inclusion.
3) The inclusions in the submerged arc weld metals are from about 0.2 to 0.4 μ in diameter, and are distributed at a mean interval of about 4μ in length. These inclusions decrease the both strengthes and increase the creep rupture elongation.
4) The hardness and the tensile rupture elongation for the lower heat input submerged arc weld metal are high compared with those for the higher heat input submerged arc weld metal.
5) Structures of solidification, dendrite, δ ferrite network for the low heat input submerged arc weld metal are fine compared with those for the high heat input submerged arc weld metal.
It is supposed that these fine structures increase the hardness and rupture elongations at tensile test.
6) As the followed thermal cycles increase the room temperature hardness for preceded weld metals, these thermal cycles have no effects on the tensile strength at elevated temperature and creep rupture strength of the preceded weld metals. These results are caused by the disappearance of the difference in the structures between the followed and the preceded weld metals during tests at the elevated temperature.
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